HTTP/2 and HTTP/3: how to see which one your site uses, and whether it matters

HTTP/2 and HTTP/3 are two newer versions of the “conversation” between the browser and the server. Our web server (LiteSpeed) speaks HTTP/2 and advertises HTTP/3; we measured that on a site served directly by it. There is nothing to switch on in your account. What you can do is confirm your site is using them, and know what to expect from them.

How to see which protocol is in use

1 Open the site in Chrome or Edge, press F12, then the Network tab.
2 Right-click the row of column titles and switch on the Protocol column.
3 Reload the page (Ctrl+Shift+R). Each row shows h2 (HTTP/2), h3 (HTTP/3) or http/1.1 (the old one).
4 From the command line: curl -sI --http2 -o /dev/null -w "%{http_version}\n" https://yourdomain.tld/ prints 2 if it spoke HTTP/2. To see whether the server advertises HTTP/3, look for the alt-svc line in the headers: if it says h3, it does.

Note that the first request usually goes over h2 and only the later ones move to h3: the server announces h3 in that first reply, and the browser switches afterwards. So a freshly opened page may show h2 and a reload h3.

What changes, and what does not

Version What it brings What it does not do
HTTP/1.1 One request at a time per connection. Forces tricks such as joining files to save requests.
HTTP/2 Many files at once over the same connection. Joining CSS and JS stops paying off. Does not turn a heavy page into a fast one.
HTTP/3 Runs over QUIC (UDP). Recovers better from drops on unstable networks, such as mobile. Does not help when the problem is a huge image or a server slow to answer.

If your site shows http/1.1

On a site with HTTPS that is unusual. Check the causes, most likely first:

1 The address is http, not https. Browsers only use h2 and h3 over HTTPS. Check the padlock and the redirect. See mixed content after moving to HTTPS.
2 A service in front of the site (such as Cloudflare) talks to the visitor on its own: what the column shows is what it offers, not what our server offers. See Cloudflare: when it helps and how to switch it on.
3 An antivirus or a company network inspecting traffic can force http/1.1. Try another network.
4 None of these? Open a support ticket with the address and what the column shows.
HTTP/3 can be blocked on the visitor’s network. It uses UDP port 443, and some company and school networks block it. The browser then falls back to h2 without telling anyone. It is not a fault of the site.
Do not expect miracles. A newer protocol helps with transport, not with content. If the page is slow, the causes are the usual ones: see what actually makes a difference on a slow site.

The Protocol column shows http/1.1 on an HTTPS site and you cannot see why? Send us the address.

Open a support ticket

SEE ALSO

Gzip or Brotli: which one your visitors get

The site is slow: what actually makes a difference

Cloudflare: when it helps and how to switch it on

Hosting plans and what each includes

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